Huge delay in RC control

[F33RNI]

I wired everything according to the instructions

My setup:

Air PI:

• Raspberry PI Zero v1.3
• Raspberry Camera Rev. 1.3
• D-Link DWA-123 with RT5372 chipset

Ground PI:

• Raspberry PI 3B
• 2x MT7601 noname cards

Everything works fine after launch. Video latency is very low, as in all examples. Telemetry (Mavlink) is also transmitted without delays successfully.
But, I want to set up RC control. I connected my FlySky I6X via USB to the Ground PI and Air Pi to the Flight controller.
In wifibroadcast-1.txt (on Air PI and Ground PI) I put:
RC=ibus
CTS_PROTECTION=Y
FC_RC_BAUDRATE=115200
In the Betaflight settings, I chose IBUS and speed 115200.

After starting, the RC works, but WITH A HUGE DELAY. ~5 seconds pass after the stick position changes are accepted by the flight controller! I tried to change the bitrate and UPDATE_NTH_TIME, but it did not help.

Pls help